JP3114078B2 - Alkaline battery separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates are those relating to the separator <br/> over data for alkaline batteries.

[0002]

2. Description of the Related Art Conventionally, as a separator for an alkaline battery, a non-woven fabric made of a polyolefin-based fiber which has been subjected to sulfonation treatment to impart hydrophilicity has been used. In addition, in an alkaline secondary battery, a violent battery reaction occurs in an electrolytic solution from room temperature to around 80 ° C.,
Durability is required for an alkaline battery separator. Therefore, various types of polyolefin-based separators have been studied as substitutes for polyamide-based separators, which are inferior in durability, as separators for alkaline batteries.

Polyolefin fibers such as polyethylene and polypropylene fibers have good chemical resistance such as alkali resistance and oxidation resistance, but have very poor hydrophilicity, and thus have poor affinity for an electrolytic solution. It has a major drawback of being inferior. In order to solve this drawback, the use of ethylene-vinyl alcohol copolymer fiber (Japanese Patent Application Laid-Open
No. 34849) and those obtained by sulfonating polyethylene fibers or polypropylene fibers (for example, JP-A-57-191956, JP-A-1-132042, etc.).

[0004]

The separator using the above-mentioned ethylene-vinyl alcohol copolymer fiber has good hydrophilicity, but has insufficient oxidation resistance and poor durability. Further, the separator for an alkaline battery obtained by sulfonating the polyethylene fiber or the polypropylene fiber has a high temperature (100 to
(120 ° C.) with fuming sulfuric acid or concentrated sulfuric acid. However, since the reaction efficiency of the hydrogen exchange reaction of tertiary carbon is low, the fiber surface is deteriorated by the sulfonation treatment over a long period of time, and as a separator, There was a problem that the strength was reduced.

An object of the present invention has been made in order to solve the above problems of the prior art, more durable, and without causing fiber degradation due to sulfonation treatment, efficiently sulfone group, moreover to provide a separators for alkaline batteries which can be introduced stably.

[0006]

, There is provided a solution for the] That is, the present onset Ming, hydrophilic
30% by weight or more of core-sheath type composite fiber
A separator comprising a refining fiber, wherein the core
Sheath composite fibers, - _{[CH 2 -C (SO 3 H)} (COO
H)] - a first Ingredient is a polyolefin-based random copolymer containing a unit represented by a sea structure, melting point 25
The second component, which is a polyolefin resin having a temperature of less than 0 ° C., is
And the sheath portion constituted by was granulated sea-island port Rimaaroi, sheath
And a core made of the same resin.
And features .

[0007] that make up the sheath, the first component and island sea structure
Is not particularly limited mixing ratio of the second component of the structure, the first component of the sea structures is 50% or more by Weight ratio
If preferred particularly good hydrophilic property can be obtained.

It is preferable that the proportion of the ethylene carboxylic acid to which the sulfone group is added is in the range of 0.4 to 4 mol% in the first component. In other words, when the content is less than 0.4 mol%, the hydrophilicity is poor, and when the content is more than 4 mol%, the hydrophilicity is improved, but the chemical resistance is lowered, and thus it is unsuitable as the battery separator material of the present invention. It becomes something.

The alkaline battery separator of the present invention is characterized in that the core-sheath conjugate fiber having a specific structure having the hydrophilic property is prepared by mixing 3
When the hydrophilic composite fiber is less than 30% by weight, sufficient hydrophilicity cannot be obtained, and the present invention provides a heat-bonded nonwoven fabric containing 0% by weight or more and other polyolefin-based fibers. It becomes unsuitable as a battery separator material.

By the way, the separator for an alkaline battery of the present invention
Regulator is - [CH ₂ -CH (COOH)] - a first and Ingredient a sea structure, a polyolefin resin melting point less than 2 50 ° C. units is a polyolefin-based random copolymer containing represented by the A sheath composed of a sea-island type polymer alloy having two components in an island structure, and the same as the second component of the sheath.
A non-woven fabric comprising a core-in-sheath composite fiber comprising a core portion made of one resin, by sulfonation treatment,
It can be produced by introducing a sulfone group into the tertiary carbon portion of the main chain to which the carboxyl group in the component is bonded.
Wear.

The sulfonation treatment method and treatment conditions are not particularly limited, but-[CH ₂ -CH (C) in the first component of the polyolefin resin used in the present invention.
OOH)]-is 30 to 90 since a sulfone group can be rapidly and stably introduced under relatively mild reaction conditions.
Conditions in which the deterioration of the fibers constituting the separator does not progress, such as treatment in a concentrated sulfuric acid bath at 3 ° C., low-temperature treatment (40 ° C. or less) with 3 to 20% fuming sulfuric acid, and dry treatment with 1 to 10% by volume SO ₃ gas. Even with the sulfonation treatment that satisfies, it is possible to impart sufficient hydrophilicity.

[0012] Incidentally, in the sheath component is sulfonated a first component - [CH ₂ -CH (COOH)] -
The sulfonation treatment conditions can be arbitrarily set by appropriately changing the weight mixing ratio with the polyolefin-based resin that is difficult to be sulfonated as the second component, that is, has low sulfonation reactivity. That is, if the weight ratio of the second component is larger than that of the first component, a fiber that is strong against the sulfonation treatment can be obtained. Therefore, the sulfonation treatment conditions are relatively gently controlled without strict control. Can be set. Conversely, if the weight ratio of the first component is larger than that of the second component, sufficient hydrophilicity can be imparted even under the minimum necessary sulfonation treatment conditions under which the fiber deterioration does not proceed as described above. Can be.

[0013]

According to the present invention,-[CH ₂ C (SO ₃ H)
(COOH)]-The first component which is a polyolefin-based resin and the second component which is a polyolefin-based resin containing a unit represented by-are partially present on the surface of the fiber constituting the nonwoven fabric, so that the entirety is obtained. An alkaline battery separator having uniform hydrophilicity and uniform strength can be formed. Therefore, hydrophilicity and chemical resistance can be suitably imparted to the separator, and a separator having excellent durability can be obtained.

[0014]

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail. Example 1 Referring to FIG. 1, the sheath component was ethylene-acrylic acid copolymer resin (1) (the copolymerization ratio of acrylic acid was 1.
7 mol%, melting point 99 ° C) 70%, polypropylene resin
(2) A core-in-sheath type composite fiber (core / sheath constituent weight ratio: 50/50, 2) comprising a sea-island type polymer alloy having a weight mixing ratio of 30% and a core component comprising a polypropylene resin (3).
d × 51 mm), 60% by weight, and a sheath-core composite fiber composed of a polyethylene resin as a sheath component and a polypropylene resin as a core component (core / sheath constituent weight ratio; 50/50, 0.9)
d × 38 mm) A fiber assembly formed by uniformly opening and laminating a mixed fiber of 40% by weight was passed through a hot-air drying oven adjusted to 135 ° C., and then pressed by a cooling roll to obtain a basis weight 63.
g / m ^2, to obtain a thermal bonding nonwoven sheet having a thickness of 0.20 mm.

Subsequently, the nonwoven fabric sheet is immersed in 6% fuming sulfuric acid at 40 ° C. for 2 minutes, immersed in dilute sulfuric acid, washed with a large amount of water, neutralized with dilute ammonia water, and further thoroughly washed. And dried to obtain an alkaline battery separator according to the present invention.

EXAMPLE 2 Referring to FIG. 2, the sheath component
Ethylene-acrylic acid copolymer resin (1) (Acrylic acid copolymerization ratio: 2.9 mol%, melting point: 97 ° C) 70%, Polyethylene resin (4): 30% by weight of sea-island polymer alloy , The core component is polypropylene resin (3)
Core-sheath composite fiber (core / sheath composition weight ratio; 5
0/50, 2d × 51 mm) 50% by weight, and a sheath-core composite fiber (core / sheath constituent weight ratio; 50 /
50, 0.9d × 38 mm) A fiber assembly formed by uniformly opening and laminating a mixed fiber of 50% by weight was produced under the same processing conditions as in Example 1 with a basis weight of 63 g / m ² and a thickness of 0.20 mm.
Was obtained.

Next, the nonwoven fabric sheet is treated for one minute in a mixed gas with dry air adjusted to 30 ° C. and having an SO ₃ gas concentration of 5 vol. 1%, washed with a large amount of water, and diluted with dilute ammonia water. The resultant was subjected to a neutralization treatment, further sufficiently washed, and dried to obtain a separator for an alkaline battery according to the present invention.

Example 3 The heat-adhesive nonwoven sheet obtained in Example 1 was immersed in fuming sulfuric acid at 80 ° C. and 6% for 2 minutes, then washed with a large amount of water through dilute sulfuric acid, and dried. Thus, an alkaline battery separator according to the present invention was obtained.

Comparative Example 1 A core-sheath type composite fiber (core / sheath constituent weight ratio: 50% by weight of regular polypropylene fiber (2d × 51 mm), a sheath component made of polyethylene resin, and a core component made of polypropylene resin) 50/50,
0.9 d × 38 mm) A fiber aggregate formed by uniformly opening and laminating 50% by weight of a mixed fiber was heat-adhesive with a basis weight of 63 g / m ² and a thickness of 0.20 mm under the same processing conditions as in Example 1. A non-woven sheet was obtained.

Next, the nonwoven fabric sheet was treated under the same sulfonation processing conditions as in Example 1 to obtain a separator for an alkaline battery of Comparative Example 1.

Comparative Example 2 The heat-bondable nonwoven fabric sheet obtained in Comparative Example 1 was treated under the same sulfonation processing conditions as in Example 2 to obtain an alkaline battery separator of Comparative Example 2.

Comparative Example 3 The sheath component was an ethylene-acrylic acid copolymer resin (the copolymer ratio of acrylic acid was 2.9).
Mol%, melting point 97 ° C.), and the core component is 60% by weight of a core-sheath composite fiber (core / sheath constituent weight ratio; 50/50, 2d × 51 mm) composed of polypropylene resin, and the sheath component is polyethylene. Core-sheath type composite fiber in which the resin and the core component are made of polypropylene resin (core / sheath constituent weight ratio;
Example 1 was a fiber aggregate obtained by uniformly opening and laminating a mixed fiber of 50/50, 0.9d × 38 mm) and 40% by weight.
66g / m ² , thickness 0.2
A 0 mm heat-bondable nonwoven fabric sheet was obtained.

Next, the nonwoven fabric sheet was treated under the same sulfonation processing conditions as in Example 3 to obtain a separator for an alkaline battery of Comparative Example 3. Table 1 below shows the results of a comparison test of various physical properties of the alkaline battery separators obtained in Examples and Comparative Examples.

[0025]

[Table 1]

The test method of the test items in the table is as follows. Moisture ratio: Moisture ratio when left at 20 ° C. and RH 65% for 24 hours. Liquid absorption speed; One end of a separator material having a sample width of 25 mm was immersed in a caustic potassium solution having a specific gravity of 1.30, and the liquid absorption height after 30 minutes. Liquid retention ratio: The separator material was immersed in a caustic potassium solution having a specific gravity of 1.30, hung up for 10 minutes, and drained to remove the solution. Alkali resistance; 80 ° C in caustic potassium solution with specific gravity of 1.30
Weight reduction rate after immersion for 30 days at Oxidation resistance: 50 ° C. in a mixture of 250 ml of a 5% KMnO ₄ solution and 50 ml of a caustic potassium solution having a specific gravity of 1.30.
Weight loss after immersion for 1 hour. Strength retention: The separator tensile strength retention before and after the sulfonation treatment.

FIG. 3 shows the results of a test in which the alkaline battery separators obtained in Examples 1, 2, 3 and Comparative Examples 1, 2, 3 were incorporated into a Ni-Cd battery having a capacity of 1200 mA · hr. Show. As shown in FIG.
(Charge condition: 400 mA × 4 hr,
Discharge conditions: 1 Ω constant resistance discharge × 2 hr) As a result of the test, those using the non-woven fabric separators of Examples 1, 2, and 3 showed 100% capacity retention rate even after repeated charging and discharging 1500 times. On the other hand, when the nonwoven fabric separators of Comparative Examples 1, 2, and 3 were used, charge and discharge were repeated 800 times, the capacity was reduced, and an early capacity reduction phenomenon was observed. this is,
It is considered that the cause is liquid leakage due to an increase in internal pressure, which is considered to be caused by poor hydrophilicity due to deterioration of the fiber surface, and dry-up of the separator material.

[0028]

As described above, the separator for an alkaline battery according to the present invention has the above-mentioned structure, so that the surface of the fibers constituting the separator can be uniformly and stably sulfonated in most parts.
Liquid absorption and electrolyte affinity are maintained over a long period of time. In addition, the sulfonation treatment can be performed uniformly and stably under relatively mild processing conditions, and the fiber deterioration due to the treatment is extremely small, so that a high capacity can be maintained in repeated charge / discharge for a long time, and the battery life is greatly extended. It has various effects such as improvement.

[Brief description of the drawings]

FIG. 1 is a perspective view of a conjugate fiber used in Example 1.

FIG. 2 is a perspective view of a conjugate fiber used in Example 2.

FIG. 3 is a curve diagram showing a change in a discharge capacity retention ratio with respect to the number of charge / discharge repetitions.

[Explanation of symbols]

 1 ethylene-acrylic acid copolymer resin 2,3 polypropylene resin 4 polyethylene resin

Claims (1)

(57) [Claims] 1. A core-sheath type composite fiber having hydrophilicity of 30 wt.
% And other polyolefin-based fibers
Wherein the core-sheath composite fiber is- [CH ₂ -C
(SO ₃ H) (COOH)] - a first Ingredient is a polyolefin-based random copolymer containing a unit represented by the
A sea structure, a sheath for a second component composed of a sea-island port Rimaaroi that the island structure is a polyolefin-based resin melting point lower than 2 50 ° C., is constituted by the second component and the same resin of the sheath portion
A separator for an alkaline battery, comprising: